1) the diameter of the drill string shall not exceed the allowable value of the electric drill.

2) the drill must be clamped with the key. Do not use other tools to hit the drill chuck.

3) do not exert too much force when drilling, to prevent the motor from being overloaded. If the speed is found to be decreased, the power should be cut off immediately.

4) the piecemeal workpiece must be firmly fixed on the fixture.

5) no gloves.